Two assay development studies are included in this project: CD34+ cell quantitation: A study comparing the Biometric Imaging assay, microvolume fluorimetry (MVF), to flow cytometry (FC) for quantitation of hematopoietic cells was published in August 1997 (Read et al. J Hematotherapy 1997:6:291-301). This study demonstrated the potential utility of the MVF method as a simpler, faster alternative to standard FC methods for product quality control and for clinical decision-making about the timing and duration of stem cell apheresis. Over the past 18 months, plans were made to evaluate the final clinical CD34 assay configuration in a clinical trial. However, device malfunction and, later, unavailability of assay kits (related to patent issues) led to postponement of this study until FY 1999. This assay will resume in July 1999 and continue into FY 2000. Megakaryocyte progenitor cell colony (CFU-Mk) quantitation: A study evaluating the utility of CFU-Mk quantitation by the Megacult system (StemCell Technologies, Inc., Vancouver, BC, Canada) for quality assessment of G-CSF mobilized peripheral blood stem cell (PBSC) products was initiated in December 1998. Preliminary data show that CFU-Mk content of PBSC products is highly correlated with CD34+ cell content. On-going studies will evaluate the relationships between these product assays and platelet engraftment after transplantation, so the clinical utility of the assay can be assessed.